WASHINGTON -LRB- CNN -RRB- -- The world 's population is forecast to hit 7 billion in 2011 , the vast majority of its growth coming in developing and , in many cases , the poorest nations , a report released Wednesday said .

Riders cram into a train last month in New Delhi , India . India 's population is expected to be 1.7 billion by 2050 .

A staggering 97 percent of global growth over the next 40 years will happen in Asia , Africa , Latin America and the Caribbean , according to the Population Reference Bureau 's 2009 World Population Data Sheet .

`` The great bulk of today 's 1.2 billion youth -- nearly 90 percent -- are in developing countries , '' said Carl Haub , a co-author of the report . Eight in 10 of those youth live in Africa and Asia .

`` During the next few decades , these young people will most likely continue the current trend of moving from rural areas to cities in search of education and training opportunities , gainful employment , and adequate health care , '' Haub continued , calling it one of the major social questions of the next few decades .

In the developed world , the United States and Canada will account for most of the growth -- half from immigration and half from a natural increase in the population -- births minus deaths , according to the report .

High fertility rates and a young population base in the developing world will fuel most of the growth , especially in Africa , where women often give birth to six or seven children over a lifetime , the report says . The number is about two in the United States and 1.5 in Canada .

A stark contrast can be drawn between Uganda and Canada , which currently have about 34 million and 31 million residents , respectively . By 2050 , Canada 's population is projected to be 42 million , while Uganda 's is expected to soar to 96 million , more than tripling .

`` Even with declining fertility rates in many countries , world population is still growing at a rapid rate , '' said Bill Butz , president of the bureau . `` The increase from 6 billion to 7 billion is likely to take 12 years , as did the increase from 5 billion to 6 billion . Both events are unprecedented in world history . ''

By 2050 , India is projected to be the world 's most populous nation at 1.7 billion , overtaking current leader China , which is forecast to hit 1.4 billion . The United States is expected to reach 439 million for No. 3 on the list .

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Global population to reach 7 billion in two years , research institute projects

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Most growth is occurring in developing and poor nations , study finds

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Uganda 's population expected to almost triple by 2050

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India projected to overtake China as most populous country